Field of the Invention
The invention relates to a device for processing and storing data, in particular a chip card, having a first interface with contacts and a second contactless interface for receiving energy or power from and for communication with a terminal device, a nonvolatile semiconductor memory, a controllable switching device through which either the first or the second interface can be connected to the semiconductor memory through address, data and control lines, and a logic circuit which drives the controllable switching device.
Such a device is known from German Patent DE 39 35 364 C1. The combined chip card disclosed therein can be supplied with power both by galvanic contacting and contactlessly by inductive coupling through the use of a transmitting unit. Data exchange also takes place by both types of transmission, with power and data being fed from the contact interface directly through a multiplexer to a processing unit and a memory, whereas in the case of the contactless type of transmission a circuit which is disposed between the inductive interface and the multiplexer obtains the data and a d.c. voltage from a radio-frequency signal that is received, or modulates a carrier signal to be transmitted with a data signal in order to feed the signals through the multiplexer to the processing unit and the memory or to receive them from there.
The form of such combined chip cards is admittedly customary nowadays, but other forms of such devices are also conceivable for the processing and storing of data. Keys are also currently in common use and watches have also been proposed. A conceivable possible use of such combined chip cards is to be seen in local transport, where passengers have a card in their pocket or bag with a memory storing a value of money that is reduced by the price of the journey through the contactless type of transmission when they board a type of transport. After the value of the money has been used up, the memory can be "recharged" at a bank terminal, preferably by the type of transmission with contacts, in such a way that the same amount is debited from a current account or has to be inserted in cash.
However, in the case of the known chip card both types of transmission are of entirely equal ranking and, moreover, the multiplexer is automatically switched over to that type of transmission from which the higher supply voltage is coming.
In the case of almost all of the forms in which the known chip card is used, in which a datum stored in the memory corresponds to a value of money that may be used for paying for goods or services and which can be increased again at a bank terminal, for example, in order to make it possible to reuse the card, it is desirable however if this "recharging" is possible only by the type of transmission with contacts. The "recharging" of the card is a highly sensitive operation which necessitates a series of security precautions that cannot be accomplished in contactless data transmissions, since it is not even possible to construct the device for transmission in such a way that it is immune to interception. However, in the case of the type of transmission with contacts, it is already known to allow communication between a card and a terminal in which the card is inserted to be established only when the card is inaccessible in a lockable insert compartment of the terminal.